(a) Field of the Invention
The present invention relates to a method of measuring the radiation characteristic of an antenna, and more particularly, to an antenna radiation measurement method that scans a charging frequency and a measurement frequency in a separate manner so as to significantly enhance the intensity of measured signals.
(b) Description of the Related Art
Generally, among the antenna ranges that are used to measure the radiation characteristic (the phase, the intensity, or the amplitude) of an antenna, there are a far-field range where the measurement is made while the source antenna is placed far from the tester or receiver antenna, a near-field range where the measurement is made by using the source antenna as a transmitter and taking samples near the source antenna with a probe at a predetermined distance, and a compact range where the measurement is made while the source antenna is placed near a reflector antenna being the tester antenna.
The far-field ranges are further classified into an elevated range where the measurement is made while the source antenna and the tester antenna are installed at a tower, a building, or the top of a hill, a slant range where the measurement is made while one of the source and the tester antennas is placed at a high position and the other on the ground, and an anechoic chamber where the measurement is made in a room having surfaces with absorbent materials for removing possible reflection. The elevated range and the slant range involve lower installation and measurement costs, but practically require a very wide area and a high tower, with the disadvantage of being significantly influenced by weather. The anechoic chamber involves indoor measurement and is not influenced by weather, but has the disadvantage that much cost is needed to make a large laboratory (for example, making it with a vertical length of 10 m, a horizontal length of 10 m and a height of 5 m) with absorbent materials.
With the case of the elevated range or the slant range, the distance between the source and tester antennas is large. Further, when various objects such as trees, forests, hills, rivers, and buildings exist between the source antenna and the tester antenna, it is very difficult to make correct measurements and to quickly cope with variable measurement situations. Consequently, the measured values are largely differentiated due to the temperature differences and the weather. Moreover, with the case of the far-field range, the source antenna is exposed to the outside to correctly obtain the measured values, and hence, it becomes difficult for radar or military antennas to make the desired measurement with stealth.
The compact range is desirably installed within a relatively small space, but it undesirably requires a large-scale reflector.
With the compact range, the measurement may be made in a very small space provided that the inter-distance of minimally 1 wavelength is made to the source antenna. However, as the probe should precisely move in the X and Y axial directions to correctly configure a predetermined plane (the plane perpendicular to the central axis of the source antenna) within the short distance, much cost and time are consumed to provide the equipment for moving the probe (the tester antenna), and to make the desired measurement.
The anechoic chamber also involves the same problem as with the near-field range in that the measurement is made using a probe.
That is, with the case of the near-field range and the anechoic chamber, as the data measured at the probe are converted into far-field range data, the correct data can be obtained only when the probe moves very precisely. The precision degree in the movement of the probe reaches several micrometers (μm) to several tens of micrometers (μm). As the carrier for moving the probe very precisely is very expensive at up to hundreds of millions of won, it is practically difficult for small companies to conduct measurement experiments related to the development of antennas in a sufficient manner.
As the measurement is made while moving the probe minutely, several hours are consumed even to make the measurement once, and this means that considerable time is needed to complete the required measurements. Furthermore, as the possibility of making errors in the measuring is high due to variable environmental conditions, total inspection with respect to the produced antennas becomes impossible, and only sampling tests can be performed.
In order to obtain more accurate far-field range data, it is required to enlarge the mobile range (the plane area) of the probe, but such enlargement is practically restricted due to the limit of the carrier for moving the probe.
Furthermore, the carrier for moving the probe is liable to generate electromagnetic waves, which are applied to the measured values as noise.
Furthermore, with the case of the near-field range and the anechoic chamber, as the measurement is made only with respect to the front side of the source antenna, it is impossible to make correct expressions for a back lobe. In order to correctly express the back lobe, it is necessary to reverse the direction the source antenna and make the measurement again, and this involves doubling the measurement time.
Korean Patent No. 10-0543725 discloses a system and a method for measuring the radiation characteristic of an antenna that measures the radiation characteristic of a source antenna within a short period of time by using an ultra-mini measurement antenna and IC chips.
It is possible to measure the radiation characteristic of an antenna in real time with the Patent No. 10-0543725 as the measurement values for the entire area of a tester body are obtained simultaneously with the operation of the source antenna.
Furthermore, with the Patent No. 10-0543725, the cost reduction effect is very great, and the measurement is made without making errors due to weather or temperature variations, compared with the probe technique.
However, with the case of the Patent No. 10-0543725, as the frequency signals received by the measurement module to make the measurement is used as driving power, it may be difficult to obtain desired driving power when the measurement frequency signals are low in level. Accordingly, the measured signals transmitted from the measurement modules are weak, and a degree of amplification of several times should be conducted in order to receive and process the measured signals. Furthermore, signal distortion may occur during the amplification process.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.